Non-proliferative (non-replicating) recombinant lentiviral vectors are used in a number of studies as a vector for gene therapy to treat various diseases, such as in a system which transports a target gene to a non-dividing cell in the central nervous system (CNS) and maintains its expression over a long period of time (Non-Patent Literatures 1-4). In particular, a primate lentiviral vector from HIV-1 (human immunodeficiency virus type 1) is the most proven vector for gene therapy (Non-Patent Literatures 5-8). However, it is well known that the lentiviral vector has a risk of inducing cancer because it will be integrated into chromosomes. Especially, cases have been reported where leukemia developed in the gene therapy of haematologic diseases. It has been therefore desired to selectively transfer the gene into the neurons in order to reduce the risk of occurrence of cancer and to develop a safer vector system in the gene therapy of nervous diseases.
On the other hand, for gene therapy of a certain cranial nerve disease, useful is a viral vector which can infect a nerve terminal, is retrogradely transported through an axon and introduce a target gene into a cell body in a target site located far from the infected site (FIG. 1).
To date, a retrograde transport system in the brain of cynomolgus monkey was developed using a recombinant HIV-1 virus which uses (is pseudotyped by) a vesicular stomatitis virus (VSV) glycoprotein (VSV-G) as an envelope glycoprotein (an envelope gene protein), but the retrograde transportation of the vector was not efficient (Non-Patent Literature 9). In the method described in the reference, very few cells in the central nervous system were retrogradely infected with the recombinant HIV-1 virus injected into the striatum of the monkey, as indicated by immunostaining.
On the other hand, rabies virus (RV) is known to have an activity that RV infects a synapse terminal, and is retrogradely transported through an axon. Indeed, there is a report that a retrograde transportation ability of a non-primate lentiviral vector based on equine anemia virus was promoted by RV-G (Non-Patent Literatures 10 and 11, and Patent Literature 1).
Further, HIV-1 lentivirus pseudotyped by RV-G has been reported (Non-patent Literature 3), but, in that report, an animal experiment (in vivo) was not actually conducted using that viral vector. In addition, gene transfer in CNS with a HIV-1 vector pseudotyped by a glycoprotein from Mokola lyssavirus, a neurotropic virus causing rabies, or VSV-G, has been studied. As a result of the nasal injection of the HIV-1 vector pseudotyped by the Mokola lyssavirus glycoprotein or VSV-G into a rat, these vectors were mutually comparable with regard to retrograde transportation to the olfactory nerve system (Non-Patent Literature 12). In addition, in that literature, an example in which a viral vector was administered through striatum was not described.
To date, the present inventors have revealed that highly-frequent retrograde gene transfer at various regions in the brain can be feasible by preparing a HIV-1 lentivirus vectors pseudotyped by rabies virus glycoprotein gene (RV-G) (RV-G/HIV-1 vector) (Patent Literature 2, Hum. Gene Ther., 2007). Furthermore, said inventor prepared the fused glycoprotein (FuG-B) wherein an intracellular domain of RV-G was replaced by that of VSV-G, and succeeded in constructing a lentiviral vector system that had a higher titer (functional titer) while sustaining an excellent (highly efficient) retrograde transport ability so as to significantly increase the frequency of retrograde gene transfer or introduction (Hum. Gene Ther., 2010).